Object type & show on

Where are you trying to avoid the code duplication on? The template files themselves? or the metabox setup?

If the templates, you could always create some functions that return what you need, and the parameters could help with conditionally determining what to return. Then all you’d need to do is call the functions in the right place and pass in the right parameters.

Otherwise, some extra detail about what you’re trying to do would help me out.

As far as the templates go I have written a common function e.g. display_common_meta(), thats not the issue.

So I really only want to define one meta box and use that on the CPTs and on a specific page tempate.

At the moment I have duplicated the CMB set ups using a common meta one for the page template and one for the CPTs.

I have done it the cut and paste method in setting up the CMBs, which is fine as long as you remember to change the metabox id.

Of course a neater way would be to write a show_on_db function to detect the template only if it is a page not a CPT. I’ll think about it when I have a moment and post back here if I work out the code.

I have to wonder if you’re getting mixed results because CPTs don’t have the dropdown option for template like the “Page” post type does.

Since you’re trying to reduce code duplication, I’d try creating an array that has all of the common values between the two, and then use that to create 2 new variables that get the different values added afterwards.

That way you only have to edit the common values once. Very basic example below.

$args_common = array(
	'value_one' => 'Value 1'
);

$cmb1 = $args_common;
$cmb2 = $args_common;
$cmb1['value_two'] = 'Value 2';
$cmb2['value_two'] = 'Value two';

You could then pass $cmb1 and $cmb2 into the respective methods to add.